1. Field of the Invention
This invention relates to a novel synthetic crystalline molecular sieve material, MCM-65, a process for its preparation and its use in hydrocarbon conversion.
2. Description of the Prior Art
Zeolitic materials, both natural and synthetic, have been demonstrated in the past to have catalytic properties for various types of hydrocarbon conversion. Certain zeolitic materials are ordered, porous crystalline aluminosilicates having a definite crystalline structure as determined by X-ray diffraction, within which there are a large number of smaller cavities which may be interconnected by a number of still smaller channels or pores. These cavities and pores are uniform in size within a specific zeolitic material. Since the dimensions of these pores are such as to accept for adsorption molecules of certain dimensions while rejecting those of larger dimensions, these materials have come to be known as “molecular sieves” and are utilized in a variety of ways to take advantage of these properties.
Zeolites typically have uniform pore diameters of about 3 Angstrom to about 10 Angstrom. The chemical composition of zeolites can vary widely but they typically consist of SiO2 in which some of the Si atoms may be replaced by tetravalent atoms such as Ti or Ge, by trivalent atoms such as Al, B, Ga, Fe, or by bivalent atoms such as Be, or by a combination thereof. When there is substitution by bivalent or trivalent atoms, cations such as Na, K, Ca, NH4 or H are also present.
Zeolites include a wide variety of positive ion-containing crystalline aluminosilicates. These aluminosilicates can be described as a rigid three-dimensional framework of SiO4 and AlO4 in which the tetrahedra are cross-linked by the sharing of oxygen atoms whereby the ratio of the total aluminum and silicon atoms to oxygen atoms is 1:2. The electrovalence of the tetrahedra containing aluminum is balanced by the inclusion in the crystal of a cation, for example, an alkali metal, an alkaline earth metal cation, or an organic species such as a quaternary ammonium cation. This can be expressed wherein the ratio of aluminum to the number of various cations, such as Ca/2, Sr/2, Na, K or Li is equal to unity. One type of cation may be exchanged either entirely or partially by another type of cation utilizing ion exchange techniques in a conventional manner. By means of such cation exchange, it has been possible to vary the properties of a given aluminosilicate by suitable selection of the cation. The spaces between the tetrahedra are usually occupied by molecules of water prior to dehydration.
Prior art techniques have resulted in the formation of a great variety of synthetic aluminosilicates. These aluminosilicates have come to be designated by letter or other convenient symbols, as illustrated by zeolite A (U.S. Pat. No. 2,882,243), zeolite X (U.S. Pat. No. 2,882,244), zeolite Y (U.S. Pat. No. 3,130,007), zeolite ZK-5 (U.S. Pat. No. 3,247,195), zeolite ZK-4 (U.S. Pat. No. 3,314,752), zeolite ZSM-5 (U.S. Pat. No. 3,702,886), zeolite ZSM-11 (U.S. Pat. No. 3,709,979), and zeolite ZSM-12 (U.S. Pat. No. 3,832,449).
The ZSM-52 and its boron-containing analog, ZSM-55, are described in U.S. Pat. Nos. 4,985,223 and 5,063,037 respectively.
U.S. Pat. No. 4,637,923 describes the porous crystalline material MCM-47 and its synthesis from a reaction mixture containing a diethylated, linear diquatemary ammonium compound as the directing agent. U.S. Pat. No. 5,068,096 discloses a method for preparing MCM-47 using bis(methylpyrrolidinium)-DIQUAT-4 as the directing agent. Accordingly, the synthesis of zeolite MCM-47 has required long dimeric templates containing diquaternary ammonium compounds.
In contrast, the present invention utilizes a monomeric directing agent rather than dimeric diquat agents, and provides a new crystalline material that has excellent porosity and much improved thermal stability.